1. Field of the Invention
The present invention relates to a real image type zoom finder having a function for correcting parallax of a finder.
2. Description of the Related Art
In a general known real image type zoom finder, a Porro prism for an erecting image is arranged between an objective lens system and an eyepiece system. This real image type zoom finder is used as a finder of a lens shutter camera, etc.
In the lens shutter camera having the above real image type zoom finder, the optical axis of a photographing lens system is different from that of a finder system. Such a lens shutter camera has no problem about a photographed object located at infinity. However, such a lens shutter camera has a problem that a photographing center is shifted from the center of a visual field of the finder in the case of the photographed object located at a close distance since the optical axis of the photographing lens system is different from the optical axis of the finder system. Such a shift is called parallax.
In particular, in the lens shutter camera using a zoom lens in the photographing lens system, this parallax is severely caused on a long focal length side of this camera.
The long focal length side is a focal length on a tele-side of the zoom lens and the short focal length side is a focal length on a wide-side of the zoom lens.
Further, parallax amounts at short and long focal lengths are different from each other on a film surface. Accordingly, it is insufficient to correct parallax by using a parallax correcting method applied to a camera using a photographing lens having a single focal length.
For example, Japanese Patent Application Laying Open (KOKAI) No. 63-179340 discloses a real image type finder having a function for correcting parallax. In this real image type finder a portion of a Porro prism is constructed by a reflecting mirror and this reflecting mirror is rotated in accordance with distance information about an object so as to correct parallax. In such a method for rotating the reflecting mirror, no optical axis of the finder is perpendicular to an image plane by the rotation of the reflecting mirror, thereby reducing an image performance.
In the lens shutter camera using a zoom lens in the photographing lens system, a parallax amount on a short focal length side is different from that on a long focal length side.
When an object is photographed, it is possible to correct parallax and visualize a photographing range by moving a frame for a visual field, etc. in conformity with a distance between the photographed object and a camera after this distance is detected. However, when no distance between the photographed object and the camera is detected, it is impossible to correct parallax and confirm the range of a photographing area by a finder.
It is possible to display a mark for confirming the photographing area at a close distance in advance within the visual field. However, in the lens shutter camera using a zoom lens in the photographing lens system, the parallax amounts on the short and long focal length sides are different from each other in accordance with the focal length of the zoom lens as mentioned above. Accordingly, display positions of the mark are different from each other so that it is complicated to display the mark within the visual field.